If you believe it's a matter of choice and its the compulsion you're objecting to, do you believe the same about seatbelts in cars, mandatory speed limits or smoking in the workplace?
You may have missed the bit where I said that I wear a helmet for longer rides so have no problem with them when required, but to answer you fully -
No problems with seatbelts in cars - you're statistically better off in a car full stop, the seat belt helps that. A cyclist that gets hit by a bus, lorry or car moving at speed will be lucky to survive whether they have a helmet on or not TBH. The point is, helmets increased the survival rate of some (not all) people that hit their head in the accident, for those that were ground to a pulp by a bus or rammed into an lamp post at 40mph they made no difference at all.
In other cases the helmet has actually made things worse by getting caught under the vehicle & dragging the cyclist along. It also causes the head to hit at a more damaging angle than it otherwise would.
Glad smoking has stopped in the workplace - but that's only due to the smell.
I've been commuting 100 miles a day to work on a motorbike for over 10 years, I wear a helmet. Mainly to keep flies out of my face & to allow me to see over 69mph. It restricts my vision and hearing hugely.
It might help if I have a low speed spill in London, but I know full well that if I come off on the motorway I'm going to be ripped in half by the central reservation or run over by at least 3 cars. It's the law to wear it, but it doesn't actually increase my safety any more to do so.
What increases my safety is being aware of the conditions, what is around me and what is coming up - it could be argued that if all drivers had the same awareness there would be less accidents overall.
Road Safety is the issue. Maybe compulsory training before being allowed to cycle (good luck with that one)? Maybe increased emphasis on cyclists in the driving test? I'm not convinced that wearing a one shot piece of polystyrene on your head actually makes the blindest bit of difference and I'm not alone in that.
I can find just as many anti-helmet arguments as you can pro...
Risksense
Times 7 Cycling Myths
I think that adults should be allowed to make their own decisions about what to wear on a non-licenced, non-powered form of transport that has no sales restrictions on it.